French investigators searching for looted Jewish-owned art want to know why the tiny painting, valued at 5m (3.75m), has suddenly turned up in the hands of a French art dealer.
The completed canvas, Un Dimanche la Grande Jatte, is 9ft by 6ft and owned by the Art Institute of Chicago.
Like the finished canvas it uses the technique perfected by Seurat of painting not in brush strokes, but with thousands of tiny blobs, or points, of oil-paint.
Its recovery coincides with an exhibition in Jerusalem this week of 53 paintings seized by the Nazis in France - including another Seurat - whose legitimate owners have not been traced.
In the case of the Seurat study, the chain of ownership is reasonably well-established. It once belonged to the Jewish painter Paul Signac.
In 1945, when the Signac family tried to reclaim the painting, M. Metthey said it had been stolen by the Nazis.
Following a complaint by the heirs of the Signac family, an investigation was started by the French government agency which monitors trafficking in stolen art.
In the 1880s, the Ile de la Grande Jatte was in open countryside and a favourite spot for strolling, bathing and boating. Now known as the Ile de la Jatte, it has been engulfed by the westward sprawl of Paris.